Manufacturing a Low Profile Current Measurement Connector

ABSTRACT

A current measurement connector may include a first part and a second part. Each part may include a mount and a joint. The first and second part may be joined via the respective joints through a current transformer interposed between the first and second parts. The respective mounts may be configured to receive a current from a current source and pass the received current through the current transformer via the first and second parts inducing a current in the current transformer. The induced current may be useable to measure the current from the current source. Methods for fabricating the current measurement connector may include die casting the first and second parts and press fitting the first and second parts at the respective joints through the current transformer. Methods for use may include withstanding a fault current pulse and dissipating heat associated with the pulse via the first and second parts.

CONTINUATION AND PRIORITY DATA

This application is a continuation of U.S. application Ser. Ser. No.14/179,300, titled “Low Profile Current Measurement Connector”, filedFeb. 12, 2014, whose inventor was David R. Pasternak.

FIELD OF THE INVENTION

The present invention relates to the field of current measurement, andmore particularly to a low profile current measurement connector.

DESCRIPTION OF THE RELATED ART

Current measurement devices must be able to withstand fault current, orover-current, events in order to ensure the safety of the user and thepower grid during such events. Note that the primary safety concerns arethe excessive temperature rises caused by such events and the isolationof the PMU from such events. Therefore, the power measurement industryhas specified that current inputs to power measurement units (PMUs) mustbe able to withstand current pulses of up to two hundred and fifty timesthe nominal current transformer (CT) value for one cycle, e.g., acomplete period within an alternating current (AC) waveform. In mostcases, the nominal CT value is either 1 ampere (A) or 5 A. Thus, for a 5A nominal CT value, the current inputs of the PMU must withstand amaximum current pulse of 1250 A for one cycle. Thus, in countries usinga 50 hertz (Hz) AC waveform, the PMU must withstand a maximum currentpulse of 1250 A for 0.02 seconds.

Prior art solutions were able to withstand these maximum current pulsesonly with form factors greater than four square inches of total printedcircuit board (PCB) space. These large form factors of the prior artsolutions were caused by the need to maintain a low resistance throughthe primary windings of a CT. This need to maintain a low resistancecaused the primary windings to grow in size, i.e., cross sectional areathrough the CT needed to grow in size, to inhibit excessive temperaturerise in the device.

Furthermore, prior art solutions were only able to withstand excessivetemperatures by maintaining enough distance from the primary windings toany thermally sensitive components, further growing the overall size ofthe current measurement circuit. Thus, there is a need for smaller formfactors for current measurement devices.

SUMMARY OF THE INVENTION

Various embodiments of a low profile current measurement connector andmethods for manufacturing and using a low profile current measurementconnector are presented below. In one embodiment, a current measurementconnector may include a first part and a second part. The first part mayinclude a first mount and a first joint. In certain embodiments, thefirst part may also include one or more pins or tabs configured tocouple the first part to a printed circuit board. In such embodiments,the coupling between the first part and the printed circuit board may bemechanical only. Thus, the first part may be electrically isolated fromthe printed circuit board. The second part may include a second mountand a second joint. In one embodiment, the first part and the secondpart may be die cast from one or more of zinc, aluminum, or copper.

Additionally, the current measurement connector may include a currenttransformer. The current transformer may be interposed between the firstpart and the second part and the first part and the second part mayconnect at the first and second joints through the current transformer,thereby electrically coupling the first mount to the second mount. In anexemplary embodiment, the first and second joints may implement at leasta portion of a primary coil. In certain embodiments, the first mount andthe second mount may be configured to receive a first current from acurrent source and the current measurement connector may be configuredto pass the first current from the current source through the first andsecond joints thereby inducing a second current in the currenttransformer. The second current may be useable to measure the firstcurrent. In certain embodiments, the first mount may be furtherconfigured to electrically couple to a first wire lug via a firstthreaded fastener and the second mount may be further configured toelectrically couple to a second wire lug via a second threaded fastenerand the first and second wire lug may be electrically coupled to thecurrent source.

In certain embodiments, the first and second joints may be first andsecond cold-forming joints. Accordingly, the first part and the secondpart may connect at the first and second cold-forming joints via a pressfit.

In an exemplary embodiment, the current measurement connector may alsoinclude an overmold. The overmold may encapsulate the first and secondparts connected through the current transformer and may electricallyisolate the current measurement connector. Additionally, the overmoldmay thermally insulate the current measurement connector and maymechanically isolate the current measurement connector from mechanicalvibration.

In another embodiment, the current measurement connector may alsoinclude a spacer interposed between the first mount and the secondmount. In such embodiments, the spacer may be configured to isolate thefirst mount and second mount from mechanical vibration and prevent analternative electrical coupling between the first mount and secondmount.

In certain embodiments, the current measurement connector may be able towithstand fault current pulses, thereby protecting the currenttransformer from damage. In other embodiments, the current measurementconnector is able to dissipate heat associated with fault currentpulses, thereby protecting the current transformer from damage. In oneembodiment, the fault current pulse may be at least approximately onethousand two hundred and fifty amperes for at least approximately onecycle.

In an exemplary embodiment a method for manufacturing, or fabricating, acurrent measurement connector may include casting a first part and asecond part. The first part may include a first mount and a first joint.In certain embodiments, the first part may also include one or more tabsor pins for mounting the first part to a printed circuit board. Incertain embodiments, the one or more pins may be soldering pinsconfigured to mount to the printed circuit board via a wave solderingprocess. The second part may include a second mount and a second joint.Additionally, the first part and the second part may be joined via thefirst and second joints through a current transformer interposed betweenthe first part and the second part, thereby electrically coupling thefirst mount to the second mount, wherein the first mount and the secondmount are configured to receive a first current from a current source.Accordingly, the current measurement connector may be configured to passthe first current through the first and second joints thereby inducing asecond current in the current transformer, wherein the second current isuseable to measure the first current.

In an exemplary embodiment, the first joint may be a first cold-formingjoint and the second joint may be a second cold-forming joint, andjoining the first and second parts may also include press fitting thefirst part and the second part via the first and second cold-formingjoints.

Additionally, the method may include applying, after joining the firstand second parts, an overmold. The overmold may encapsulate the firstand second parts connected through the current transformer, electricallyisolate the current measurement connector, thermally insulate thecurrent measurement connector, and mechanically isolate the currentmeasurement connector from mechanical vibration.

In one embodiment, joining the first and second parts may also includeinterposing a spacer between the first mount and the second mount. Thespacer may be configured to isolate the first mount and second mountfrom mechanical vibration and prevent an alternative electrical couplingbetween the first mount and second mount.

In another embodiment, the method may also include plating the first andsecond parts with tin, where the tin prevents galvanic corrosion of thefirst and second mounts. Additionally, in one embodiment, the first partand the second part may be die cast from one or more of zinc, aluminum,or copper.

In an exemplary embodiment for a method for measuring current, themethod may include connecting a current source to a current measurementconnector via a first and second mount of the current measurementconnector. The current measurement connector may include a first partand a second part and the first part and the second part may connect atrespective cold-forming joints through a current transformer that may beinterposed between the first and second parts. Additionally, a firstcurrent from the current source may be passed, via the currentmeasurement connector, through the respective cold-forming jointsthereby inducing a second current in the current transformer. The secondcurrent is useable to measure the first current. Further, the method mayinclude applying a fault current pulse and the fault current pulse maybe at least approximately one thousand two hundred and fifty amperes forat least approximately one cycle. Additionally, heat associated withapplying the fault current pulse may be dissipated via the first andsecond parts thereby protecting the current transformer.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1 illustrates a system for measuring current according to oneembodiment of the invention;

FIG. 2 illustrates an exemplary module that includes one embodiment ofthe invention;

FIG. 3A illustrates a first part of a low profile current measurementconnector according to an embodiment of the invention;

FIG. 3B illustrates a second part of a low profile current measurementconnector according to an embodiment of the invention;

FIG. 4 illustrates an exploded view of a low profile current measurementconnector according to an embodiment of the invention;

FIG. 5 illustrates an assembled view of a low profile currentmeasurement connector according to one embodiment of the invention;

FIG. 6 illustrates an assembled view including an overmold of a lowprofile current measurement connector according to an embodiment of theinvention;

FIG. 7 illustrates an exemplary result of a current measurement of afault current event applied to an embodiment of the invention;

FIG. 8 illustrates an exemplary result of temperature increase due to afault current event applied to an embodiment of the invention;

FIG. 9 is a block diagram of a method of fabricating a low profilecurrent measurement connector according to an embodiment of theinvention; and

FIG. 10 is a block diagram of a method of using a low profile currentmeasurement connector according to an embodiment of the invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION Terms

The following is a glossary of terms used in the present application:

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

Measurement Device—includes instruments, data acquisition devices, smartsensors, and any of various types of devices that are configured toacquire and/or store data. A measurement device may also optionally befurther configured to analyze or process the acquired or stored data.Examples of a measurement device include an instrument, such as atraditional stand-alone “box” instrument, a computer-based instrument(instrument on a card) or external instrument, a data acquisition card,a device external to a computer that operates similarly to a dataacquisition card, a smart sensor, one or more DAQ or measurement cardsor modules in a chassis, an image acquisition device, such as an imageacquisition (or machine vision) card (also called a video capture board)or smart camera, a motion control device, a robot having machine vision,and other similar types of devices. Exemplary “stand-alone” instrumentsinclude oscilloscopes, multimeters, signal analyzers, arbitrary waveformgenerators, spectroscopes, and similar measurement, test, or automationinstruments.

A measurement device may be further configured to perform controlfunctions, e.g., in response to analysis of the acquired or stored data.For example, the measurement device may send a control signal to anexternal system, such as a motion control system or to a sensor, inresponse to particular data. A measurement device may also be configuredto perform automation functions, i.e., may receive and analyze data, andissue automation control signals in response.

Concurrent—refers to parallel execution or performance, where tasks,processes, or programs are performed in an at least partiallyoverlapping manner. For example, concurrency may be implemented using“strong” or strict parallelism, where tasks are performed (at leastpartially) in parallel on respective computational elements, or using“weak parallelism”, where the tasks are performed in an interleavedmanner, e.g., by time multiplexing of execution threads.

Approximately—refers to a value that is almost correct or exact. Forexample, approximately may refer to a value that is within 1 to 10percent of the exact (or desired) value. Thus, a fault current may havea value of approximately 1250 amperes for approximately one cycle. Insuch an instance, the actual value of the fault current may be in therange of 1125 to 1237 amperes and would be considered approximately 1250amperes. Similarly, approximately one cycle at 50 Hz (e.g., one cycleevery 0.0200 seconds) may have an actual value in the range of 50.5 (onecycle every 0.0198 seconds) to 55.6 (one cycle every 0.0180 seconds) Hzand would be considered approximately 50 Hz. It should be noted,however, that the actual threshold value (or tolerance) may beapplication dependent. For example, in one embodiment, “approximately”may mean within 0.1% of some specified or desired value, while invarious other embodiments, the threshold may be, for example, 2%, 3%,5%, and so forth, as desired or as required by the particularapplication.

Primary Coil—refers to a coil to which an input voltage is applied in aninductively coupled circuit, such as a circuit including a currenttransformer. In other words, the primary coil refers to the coil formingthe part of an electrical circuit such that changing current in itinduces a current in a neighboring circuit, i.e., current through aprimary coil induces current in a secondary coil. Additionally, itshould be noted that the current passing through the primary coil maygenerally be greater than the current induced in the secondary coil.

Secondary Coil—refers to a coil in which current is induced in it bypassing a current through another coil, i.e., the primary coil.

FIG. 1: Exemplary System for Measuring Current

FIG. 1 illustrates an exemplary system for measuring current accordingto one embodiment of the invention. As shown, system 100 may include acomputer 82 coupled to a network. Computer 82 may include a CPU, adisplay screen, memory, and one or more input devices such as a mouse orkeyboard as shown. The computer 82 may operate with one or moreinstruments, such as CompactDAQ 118 provided by National InstrumentsCorporation, to analyze, measure, or control a unit under test (UUT) orprocess 150, e.g., via execution of software 104.

As depicted, the instrument, e.g., CompactDAQ 118, may include modulesthat may include embodiments of the present invention to connect to UUT150 and measure current from a current source included in UUT 150. Note,however, that CompactDAQ 118 is only an exemplary example of a chassisthat may include or implement embodiments of the invention. It isenvisioned that embodiments of the invention may be included orimplemented in any of a variety of chassis, such as National InstrumentsCorporation's PXI chassis and CompactRIO, among others. Note further,that system 100 is exemplary only, and embodiments of the presentinvention may be used in a data acquisition and control application, ina test and measurement application, an image processing or machinevision application, a process control application, a man-machineinterface application, a simulation application, or ahardware-in-the-loop validation application, among others.

FIG. 2: Exemplary Module for Measuring Current

FIG. 2 illustrates an exemplary module for measuring current accordingto one embodiment of the invention. As shown, module 200 may be includedin a system, such as system 100. Module 200 may include a housing 202and securing tabs 204 for securing module 200 in a chassis, such asCompactDAQ 118, although any other type of instrument or chassis may beused as desired. The housing 202 may house a printed circuit board(PCB). The PCB may include circuitry for measuring current.Additionally, one or more current measurement connectors 208 may becoupled to the PCB enclosed within housing 202. In certain embodiments,current measurement connectors 208 may include a primary and a secondarycoil. In such embodiments, the primary coil may be electrically isolatedfrom the PCB. In other words, the secondary coil of the currentmeasurement connectors 208 may be electrically coupled the PCB and theprimary coil of the current measurement connectors 208 may bemechanically coupled to the PCB. Additionally, current measurementconnectors 208 may be thermally insulated from the PCB and housing 202.Hence, the PCB and housing 202 may be electrically isolated andthermally insulated from a fault current passed through the primary coilof one or more of the current measurement connectors 208. The faultcurrent may be generated by one or more current sources coupled to theone or more current measurement connectors 208 via mounting for wirelugs 206 that may be mounted to current measurement connectors 208. Thewire lugs 206 may be electrically coupled to the one or more currentmeasurement connectors 208 via threaded fasters. Further detailsregarding current measurement connectors 208 are provided below.

FIGS. 3-6: Exemplary Embodiment of a Low Profile Current MeasurementConnector

FIGS. 3-6 illustrate an exemplary embodiment of a low profile currentmeasurement connector. The current measurement connector may include atleast two parts mechanically coupled to form a primary coil through acurrent transformer. Once coupled, or joined, the at least two parts maybe electrically coupled such that a first current may be passed throughthe primary coil formed by the at least two parts to induce a secondcurrent in the current transformer. In other words, during operation,the at least two parts may form or implement a primary coil, where acurrent passing through the primary coil may induce current in asecondary coil, e.g., the coil of the current transformer. The currentinduced in the current transformer may be usable to measure the currentpassing through the primary coil.

As illustrated in FIG. 3A, a first part 300 of a current measurementconnector, such as the one or more current measurement connectors 208,may include a mount and a joint. The mount may be similar to exemplarymount 302. In one embodiment, mount 302 may be configured to couple to awire lug, such as one of wire lugs 206 of FIG. 2. In other embodiments,mount 302 may include a screw terminal or wire clamp, among other typesof mounts suitable for electrically coupling a current source to thefirst part 300. Additionally, first part 300 may include a joint 304.The joint may be any of various types including a cold-forming, orpress-fitting joint, a threaded joint, a welding joint, an adhesivejoint, or any other type of joint suitable for mechanically andelectrically coupling the first part 300 to a second part of the currentmeasurement connector (discussed below with respect to FIG. 3B) toimplement the techniques disclosed herein. In other words, the joint maybe required to electrically couple first part 300 to a second part ofthe current measurement connector, such as second part 350 discussedbelow with respect to FIG. 3B.

In certain embodiments, first part 300 may also include mounting tabs306 suitable for mechanically coupling first part 300 to a PCB. In oneembodiment, mounting tabs 306 may be one or more soldering pins. Incertain embodiments, the soldering pins may be configured to mount to aPCB via a wave soldering process. In such embodiments, the first part300 may mount to the PCB via through holes disposed in the PCB. Asillustrated, first part 300 may include one or more sets of mountingtabs 306. Thus, the first part 300 may be mechanically coupled to thePCB and may not be electrically coupled to the PCB. Of course, any othermechanical coupling means may be used as desired.

As illustrated in FIG. 3B, a second part 350 of a current measurementconnector may include a mount and a joint. The mount may be similar tomount 352 and configured to couple to a wire lug, such as wire lugs 206of FIG. 2. In some embodiments, mount 352 may include a screw terminalor wire clamp, among other types of mounts suitable for electricallycoupling a current source to the second part 350. Additionally, secondpart 350 may include a joint 354. The joint may be any of various typesincluding a cold-forming, or press-fitting joint, a threaded joint, awelding joint, an adhesive joint, or any other type of joint suitablefor mechanically and electrically coupling the second part 350 to afirst part of the current measurement connector (discussed above withrespect to FIG. 3A) to implement the techniques disclosed herein. Inother words, the joint may be required to electrically couple secondpart 350 to a first part of the current measurement connector, such asfirst part 300 discussed above with respect to FIG. 3A.

In some embodiments the first and second parts may be die cast. The diecast material used to cast the first and second part may be one of zinc,aluminum, or copper, among other die casting materials. In otherembodiments, the die cast material may be an alloy that may include oneor more of zinc, aluminum, or copper. In one particular embodiment, zincdie cast ZA-8 may be used. In another embodiment, the die cast materialmay be specified such that the die cast may be molded in thin walls,e.g., a nominal wall thickness of approximately 0.06 to 0.09 inches. Inother words, the wall thickness may be sufficiently thin to allow thedie cast part to be solderable. Additionally, the die cast material mayhave a relatively low electrical resistivity, e.g., approximately 50 to70 nano-ohm meters, in order to prevent the parts from generatingexcessive heat due to an applied current. In other words, the electricalresistivity of the parts may be sufficiently low to allow highercurrents to be applied to the parts without the generation of excessiveheat. In certain embodiments, the die cast material may have thecapability to be tin plated, which may prevent galvanic corrosion of thefirst and second mounts Also, in some embodiments, the die cast materialmay have the capability to be cold-worked. In other words, the materialmay have the capability to be strengthened via plastic deformation.Examples of cold-working, or work-hardening processes, include, amongothers, press-fitting, rolling, extruding, forging, riveting, andburnishing.

FIG. 4 illustrates an exploded view of an exemplary low profile currentmeasurement connector according to an embodiment of the invention. Asshown, current measurement connector 400 may include a first part 402, asecond part 408, a current transformer 404, and a spacer 406. The firstpart 402 may be similar to first part 300 described above in referenceto FIG. 3A. Similarly, second part 408 may be similar to second part 350described in reference to FIG. 3B. As illustrated in FIG. 4, first part402 and second part 408 may be configured to join through currenttransformer 404. In other words, the current transformer 404 may beinterposed between the first part 402 and the second part 408. Thejoining of first part 402 and second part 408 may form a primary coilthat passes through current transformer 404. Additionally, first part402 and second part 408 may be joined via any of a variety of mechanicalor chemical processes, including, among others, welding, riveting,threaded fasteners, soldering, adhesion, and cold-forming, orpress-fitting, among others. In one particular embodiment, the firstpart 402 and second part 408 are joined through the current transformer404 via a press fit. In other words, the joint may be formed in a coldforming process in which the two parts are pressed together in a coldforming, cold working, or work hardening process. In such embodiments,the joint formed may have a low resistance, e.g., approximately 100 to200 micro-ohms. In other words, the joint formed may have a sufficientlylow resistance to allow higher currents to be applied through the jointwithout the generation of excessive heat.

In certain embodiments, the spacer 406 may be interposed between a firstmount of the first part 402 and a second mount of the second part 408.In such embodiments, the spacer may be configured to isolate the firstmount and the second mount from mechanical vibrations. Additionally, inan exemplary embodiment, the spacer may be configured to prevent analternative electrical coupling between the first mount and the secondmount. In other words, the spacer may prevent the accidental shorting ofthe first mount to the second mount upon connection to a current source.For example, in a particular embodiment, the spacer may prevent a screwused to connect the current source to the first part of the currentmeasurement connector from bottoming out against the second part of thecurrent measurement connector. In other words, the screw would bottomout against the non-conductive spacer and thus prevent the screw fromshorting the first part to the second part. Additionally, in certainembodiments the spacer may stabilize the parts of the currentmeasurement connector by preventing the parts from rotating or twistingrelative to one another. Further, in one particular embodiment, thespacer may prevent the overmold (discussed below in reference to FIG. 6)from leaking or encapsulating threads that may be provided forconnecting the current source to current measurement device.

FIG. 5 illustrates an assembled view of an exemplary low profile currentmeasurement connector 500 according to an embodiment of the invention.As illustrated, current measurement connector 500 is an assembledembodiment of current connector 400 of FIG. 4, and so like orcorresponding parts are numbered accordingly. As shown, currentconnector 500 may include first part 402, current transformer 404,spacer 406, and second part 408. First part 402 may be joined to secondpart 408, thereby forming a primary coil through current transformer404. Thus, a current passed through the primary coil may induce acurrent in the current transformer which may be usable to measure thecurrent passed through the primary coil. It should be noted that thecurrent passing through the primary coil may generally be greater thanthe current induced in the secondary coil. First part 402 may includeone or more soldering pins configured to mechanically couple to a PCB.Further, current transformer 404 may include one or more soldering pins(or other coupling means) configured to electrically couple to the PCB.Thus, the primary coil, e.g., the coil formed by joining the first part402 and the second part 408 may not be electrically coupled to the PCB.

FIG. 6 illustrates an assembled view of an exemplary low profile currentmeasurement connector 600 according to an embodiment of the invention.As illustrated, current measurement connector 600 may be similar tocurrent connector 500 of FIG. 5, and may further include an overmold. Inother words, current measurement connector 600 illustrates an embodimentof current connector 500 with an overmold. The overmold may encapsulatethe first and second parts of current measurement connector.Additionally, the overmold may electrically isolate the currentmeasurement connector 600. Further, in some embodiments, the overmoldmay thermally insulate the current measurement connector. Also, theovermold may mechanically isolate the current measurement connector frommechanical vibration. In one embodiment, the overmold may be a hightemperature liquid crystal polymer plastic.

In certain embodiments, the current measurement connector may be able towithstand over current, or fault current, pulses or events. Withstandingsuch events, or pulses, may protect the current transformer that may beincluded in the current measurement connector. Additionally, the currentmeasurement connector may be able to dissipate heat associated with suchfault current pulses further protecting the current transformer fromdamage. Note further, that such heat dissipation may also protect theheat sensitive components included on a PCB that may be coupled to thecurrent measurement connector. In other words, the current measurementconnector may protect the components included in a module such as module200 described above. Thus, in one embodiment, the current measurementconnector may be able to withstand over current, or fault current,pulses or events of at least approximately one thousand two hundred andfifty amperes for at least one cycle. Note that these fault currentvalues, e.g., pulse or events, are exemplary only. In other embodiments,withstanding other fault current values, e.g., pulses or events, may benecessary, depending on the application and/or system requirements.

As used herein, the term “approximately” generally refers to a valuethat is almost correct or exact. For example, approximately may refer toa value that is within 1 to 10 percent of the exact (or desired) value.Thus, a fault current may have a value of approximately 1250 amperes forapproximately one cycle. In such an instance, the actual value of thefault current may be in the range of 1125 to 1237 amperes and would beconsidered approximately 1250 amperes. Similarly, approximately onecycle at 50 Hz (e.g., one cycle every 0.0200 seconds) may have an actualvalue in the range of 50.5 (one cycle every 0.0198 seconds) to 55.6 (onecycle every 0.0180 seconds) Hz and would be considered approximately 50Hz. However, as noted above, the actual threshold value (or tolerance)may be application dependent. For example, in one embodiment,“approximately” may mean within 0.1% of some specified or desired value,while in various other embodiments, the threshold may be, for example,2%, 3%, 5%, and so forth, as desired or as required by the particularapplication.

FIGS. 7-8 below provide exemplary results of the thermal response of anexemplary current measurement connector that includes embodiments of thepresent invention.

FIGS. 7-8: Exemplary Results of a Fault Current Event

FIGS. 7 and 8 illustrate exemplary results of a thermal test of a faultcurrent event as measured on an exemplary embodiment of the invention.As illustrated in FIG. 7, a fault current may be applied to an exemplarycurrent measurement connector configured with embodiments of the presentinvention. The fault current event, or over current event, may have anaverage value of approximately 1,000 amperes over a duration ofapproximately one second. The drop in the current over the one secondevent is a result of the resistance of the exemplary current measurementconnector increasing as the temperature of the current measurementconnector increases.

FIG. 8 illustrates a temperature response of the exemplary currentmeasurement connector in response to a current pulse. The temperature802 represents the temperature of the joined first and second parts ofthe exemplary current measurement connector. Temperature 804 representsthe internal ambient temperature of the housing that may enclose a PCBthat the exemplary current measurement connector may be coupled to.Temperature 806 represents the external ambient temperature, e.g., theroom temperature. In this particular case, the current pulse was appliedwithin the first two seconds of the temperature response measurement. Asmay be seen, temperature 802 reached a maximum temperature ofapproximately 56° C., while temperature 804 reached a maximumtemperature of approximately 32° C. The low temperature rise is a directresult of the low resistance joint and overall low resistivity of theexemplary current measurement connector, and thus illustrates a benefitof the present techniques.

FIG. 9: Block Diagram of a Method for Fabricating a Low Profile CurrentMeasurement Connector

FIG. 9 illustrates a method for manufacturing, or fabricating, a lowprofile current measurement connector according to one embodiment. Themethod of FIG. 9 may be used to fabricate any of the embodiments of thecurrent measurement connectors described in reference to the aboveFigures. In various embodiments, some of the method elements shown maybe performed concurrently, in a different order than shown, or may beomitted. Additional method elements may also be performed as desired. Asshown, this method may operate as follows.

In 902, a first part of the current measurement connector may be cast.The first part may include a first mount and a first joint, such as acold-forming joint. Alternatively, the first part may be manufactured,or fabricated, using any of various techniques, such as die casting,machining, or stamping, among others. In some exemplary embodiments, thefirst part may be die cast from one or more of: zinc, aluminum, orcopper, i.e., the die cast material may be any of these metals, or maybe an alloy that includes one or more of these metals. As noted above,in one particular embodiment, zinc die cast ZA-8 (an alloy of zinc) maybe used. In certain embodiments, the first part may also include one ormore pins or tabs for connecting the current measurement connector to aPCB. In one exemplary embodiment, the first part may include solderingpins configured to mount to the PCB via holes disposed in the PCB. Insuch embodiments, the current measurement connector may be coupled, orattached, to the PCB via a wave soldering process. Note, however, thatthe first part may not be electrically coupled to the PCB. In otherwords, the coupling between the PCB and the first part may be mechanicalonly. Accordingly, the first part may be electrically isolated (orinsulated) from the PCB.

In 904, a second part of the current measurement connector may be cast.The second part may include a second mount and a second joint, such as acold-forming joint. Alternatively, the second part may be manufactured,or fabricated, using any of various techniques, such as die casting,machining, or stamping, among others. In some exemplary embodiments, thesecond part may be die cast from one or more of: zinc, aluminum, orcopper, or an alloy that includes one or more of these metals, e.g.,zinc die cast ZA-8 (an alloy of zinc).

In 906, the first and second parts may be joined through a currenttransformer interposed between the first and second parts via the firstand second joints. Joining the first and second parts may electricallycouple the first mount to the second mount. Additionally, the first andsecond mount may be configured to receive current from a current source.Further, the current measurement connector may be configured to pass thecurrent from the current source through the first and second joints andinduce current in the current transformer useable to measure the currentreceived from the current source.

In some embodiments, the first and second joints may be cold-formingjoints. In such embodiments, joining the first and second parts may alsoinclude press fitting the first part and the second part together viathe first and second cold-forming joints. Alternatively, the first andsecond parts may be joined using any of various manufacturing techniquessuch as welding or braising, among others. For example, in someembodiments, the first and second parts may be joined using a threadedfastener or adhesive, among others techniques for fastening. In someembodiments, the technique used for joining may be particularly chosento produce low resistivity in the joint.

In some embodiments, the method may further include applying an overmoldto the current measurement connector after the first and second partshave been joined through the current transformer. The overmold mayencapsulate the first and second parts connected through the currenttransformer. Additionally, the overmold may electrically isolate thecurrent measurement connector and thermally insulate the currentmeasurement connector. Further, the overmold may mechanically isolatethe current measurement connector from mechanical vibration. In someembodiments, the overmold may be a high temperature liquid crystalpolymer plastic.

In an exemplary embodiment, joining the first part and the second partmay also include interposing a spacer between the first and secondmount. In an exemplary embodiment the spacer may be configured toisolate the first mount and second mount from mechanical vibration.Additionally, the spacer may be configured to prevent an alternativeelectrical coupling (electrical short) between the first mount andsecond mount.

In one embodiment, the method may also include plating the first andsecond parts, e.g., the first and second parts may be plated with tin,which may prevent galvanic corrosion of the first and second mounts.Other plating materials may be used as desired.

FIG. 10: Block Diagram of a Method for Measuring Current Using a LowProfile Current Measurement Connector

FIG. 10 illustrates a method for measuring current using a low profilecurrent measurement connector, according to one embodiment. The methodof FIG. 10 may be used with any of the embodiments of the currentmeasurement connectors described in reference to the above Figures. Invarious embodiments, some of the method elements shown may be performedconcurrently, in a different order than shown, or may be omitted.Additional method elements may also be performed as desired. As shown,this method may operate as follows.

In 1002, a current source may be connected to a current measurementconnector via a first and second mount of the current measurementconnector. The current measurement connector may include a first partand a second part. The first part and the second part may connect atrespective cold-forming joints through a current transformer interposedbetween the first and second parts. In certain embodiments, the currentmeasurement connector may be similar to the current measurementconnectors described above.

In 1004, a current from the current source, e.g., a first current, maybe passed through the current measurement connector. The current fromthe current source may induce a current in the current transformer,e.g., a second current. The current in the current transformer may beuseable to measure the current from the current source.

In certain embodiments, the method may also include applying a faultcurrent pulse to the current measurement connector. In some embodiments,the fault current pulse, or over current event, may be at leastapproximately one thousand two hundred and fifty amperes for at leastapproximately one cycle, although other pulse amplitudes and/ordurations may be used as desired. Note that these fault current values,e.g., pulse or events, are exemplary only. In other embodiments,withstanding other fault current values, e.g., pulses or events, may benecessary, depending on the application and/or system requirements.Additionally, note that a cycle may refer to a complete period within analternating current (AC) waveform. Thus, the cycle may last for at leastapproximately 0.02 seconds for a 50 Hz AC waveform.

Additionally, the method may include dissipating, via the first andsecond parts of the current measurement connector, heat associated withthe application of the fault current pulse. Dissipating the heatassociated with the fault current pulse may protect the currenttransformer. Additionally, dissipation of the heat associated with thefault current pulse may protect sensitive components included in ahousing of a PCB that the current measurement connector may be coupledto.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

We claim:
 1. A method for manufacturing a current measurement connector,the method comprising: casting a first part of the current measurementconnector, wherein the first part comprises: a first mount; and a firstjoint; casting a second part of the current measurement connector,wherein the second part comprises: a second mount; and a second joint;and joining the first part and the second part via the first and secondjoints through a current transformer interposed between the first partand the second part, thereby electrically coupling the first mount tothe second mount, wherein the first mount and the second mount areconfigured to receive a first current from a current source; wherein thecurrent measurement connector is configured to pass the first currentthrough the first and second joints thereby inducing a second current inthe current transformer, wherein the second current is useable tomeasure the first current.
 2. The method of claim 1, wherein the firstpart further comprises: one or more soldering pins, wherein the one ormore soldering pins are configured to mount via a wave soldering processto a printed circuit board via through holes disposed in the printedcircuit board.
 3. The method of claim 2, wherein the first part is notelectrically coupled to the printed circuit board.
 4. The method ofclaim 1, wherein the first part further comprises one or more solderingpins, the method further comprising: mounting, via a wave solderingprocess, the one or more soldering pins to a printed circuit board viathrough holes disposed in the printed circuit board.
 5. The method ofclaim 4, wherein the first part is not electrically coupled to theprinted circuit board.
 4. The method of claim 1, wherein the first jointis a first cold-forming joint, wherein the second joint is a secondcold-forming joint, and wherein said joining further comprises pressfitting the first part and the second part via the first and secondcold-forming joints.
 5. The method of claim 1, further comprising:applying, after said joining, an overmold, wherein the overmold:encapsulates the first and second parts connected through the currenttransformer; electrically isolates the current measurement connector;thermally insulates the current measurement connector; and mechanicallyisolates the current measurement connector from mechanical vibration. 6.The method of claim 1, wherein said joining further comprises:interposing a spacer between the first mount and the second mount,wherein the spacer is configured to: isolate the first mount and secondmount from mechanical vibration; and prevent an alternative electricalcoupling between the first mount and second mount.
 7. The method ofclaim 1, further comprising: plating the first and second parts withtin, wherein the tin prevents galvanic corrosion of the first and secondmounts.
 8. The method of claim 1, wherein the first part and the secondpart are die cast from one or more of zinc, aluminum, or copper.
 9. Themethod of claim 1, wherein the second part is physically separate anddistinct from the first part, and wherein the first part and the secondpart physically connect together at and via respective cold-formingjoints and extend through a current transformer interposed between thefirst and second parts.
 10. The method of claim 1, wherein the currentmeasurement connector is able to withstand fault current pulses of atleast approximately one thousand two hundred and fifty amperes for atleast approximately one cycle, thereby protecting the currenttransformer from damage.
 11. The method of claim 1, wherein the currentmeasurement connector is able to dissipate heat associated with faultcurrent pulses of at least approximately one thousand two hundred andfifty amperes for at least approximately one cycle, thereby protectingthe current transformer from damage.
 12. The method of claim 1, wherein,when connected, the first and second joints implement at least a portionof a primary coil.
 13. The method of claim 1, further comprising:electrically coupling, via a first threaded fastener, the first mount toa first wire lug; and electrically coupling, via a second threadedfastener, the second mount to a second wire lug; wherein the first andsecond wire lug are electrically coupled to the current source.